Riordan Rick: House of Hades (Heroes of Olympus #4)
House of Hades (Heroes of Olympus #4) - Rick Riordan. At the conclusion of The Mark of Athena, Annabeth and Percy tumble into a pit leading straight to the Underworld. The other five demigods have to put aside their grief and follow Percy's instructions to find the mortal side of the Doors of Death. If they can fight ...a dál?